A tollbooth is shuttered as heavy smog spreads on a highway and vehicles are forced to wait in Jilin Province, in northeast China, Oct. 22. Thick smog enveloped China’s northeast area for a third day on Oct. 22, with schools and regional airports shuttered and low visibility forcing ground transport to a halt in places. (STR/AFP/Getty Images)

China’s air pollution is so bad that it’s obscuring surveillance cameras, preventing Chinese Communist authorities from spying on people, says a new report. China has likely the most pervasive system of surveillance cameras in the world, with tens of millions set up in its cities.

China has one of the most expansive surveillance systems on Earth, but the effectiveness of its network of CCTV cameras is being imperiled due to smog that has blanketed much of the country.

According to a report from the South China Morning Post, 20 million Chinese surveillance cameras can’t see through the smog, namely in the northern city of Harbin–where visibility fell to below 10 feet on an especially polluted day in October. Local residents complained they can barely see their own hands and feet.

Kong Zilong, who is an expert in video surveillance technology, told the South China Morning Post that no CCTV cameras can sufficiently penetrate the pollution levels in China. He added that even infrared cameras can’t be used in some areas in China, where the smog is especially thick.

“According to our experience, as the visibility drops below three meters, even the best camera cannot see beyond a dozen meters,” Kong said.

The National Natural Science Foundation of China was tasked with finding a solution to the problem within four years.

“Most studies in other countries are to do with fog. In China, most people think that fog and smog can be dealt by the same method. Our preliminary research shows that the smog particles are quite different from the small water droplets of fog in terms of optical properties,” Professor Yang Aiping, who is an expert in digital imaging at the School of Electronic Information Engineering of Tianjin University, told the paper.

Earlier reports show that China spent $16 billion on video surveillance between 2009 and 2011. There are more than 800,000 CCTV cameras in Beijing alone, making it the most camera-laden city in the world.

Cameras are used to go after Chinese dissidents, such as human rights activists. Human Rights Watch said that often times, multiple cameras are directed at one dissident and their families.